Synthesis of Cs₃MnBr₅ Green Phosphors Using an Eco-Friendly Evaporative Crystallization Process

Green (G) and red (R) light-emitting materials, such as quantum dots, perovskite nanocrystals, and inorganic phosphor powders, owing to their excellent optical characteristics, have attracted researchers' attention as color-conversion materials for lighting and display applications. However, these materials contain environmentally harmful elements, such as Pb or Cd, and/or they are synthesized using environmentally harmful synthetic approaches and conditions, involving the use of organic solvents, high pressure, high temperature, harsh atmosphere, and long reaction time. In this study, as an eco-friendly synthetic approach to synthesize lead-free Cs₃MnBr₅ G powder phosphor, we suggest an evaporative crystallization process of aqueous reactant solution. This synthetic process does not use toxic elements or solvents and the crystallization process utilizes only low reaction temperature and short reaction time under air atmosphere conditions. We successfully synthesized Cs₃MnBr₅ green powder phosphor, with excellent optical properties, by evaporative heating of a 200 nm syringe-filtered solution at 150 °C for 2 h. The synthesized Cs₃MnBr₅ phosphors have a photoluminescence quantum yield of 66.3%, a peak wavelength of 520 nm, a narrow bandwidth of 38 nm, and a photoluminescence decay time of 0.34 ms under blue excitation. This phosphor is expected to be a useful alternative G-emitting material that can compete with commercial green quantum dots, perovskite nanocrystals, or inorganic phosphors.